JP2009063427A - Radio wave anechoic box - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio wave anechoic box capable of measuring the characteristics of an object to be measured for radiating electromagnetic waves at a plurality of frequency bands. <P>SOLUTION: A cylindrical member 7 capable of moving axially is provided inside a metal casing 2 and a screen member 12 capable of moving axially is provided in the cylindrical member 7. Then, radio wave absorbers 3, 5, 14 for absorbing electromagnetic waves at a frequency band of a high-frequency side are provided on a front wall surface 2A of a metal casing 2, on an inner-periphery surface, and on the front of the screen member 12, respectively. Radio wave absorbers 4, 11, 15 for absorbing electromagnetic waves at a frequency band of a low-frequency side are provided on a rear wall surface 2B of the metal casing 2, on an inner-periphery surface of the cylindrical member 7, and on the rear surface of the screen member 12, respectively. Therefore, by moving the cylindrical member 7 and the screen member 12 axially, either the radio wave absorbers 3, 5, 14 or radio wave absorbers 4, 11, 15 can be exposed to the metal casing 2 selectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an anechoic box suitable for use when measuring electromagnetic waves radiated from, for example, a mobile phone.

  In general, a radio wave anechoic box is provided with a radio wave absorption sheet or the like in a small metal casing, and a measurement object such as a mobile phone is arranged in the metal casing, and the radiation efficiency of the antenna provided on the measurement object Is known (for example, see Patent Documents 1 and 2). Patent Document 1 discloses a configuration in which a radio wave absorption sheet used in a specific frequency band is provided inside a radio anechoic box in order to provide a small and inexpensive measurement space. At this time, the radio wave absorption sheet has radio wave absorption characteristics in the measurement frequency band of electromagnetic waves. For this reason, it is the structure which uses a different electromagnetic wave absorption sheet according to the use frequency band of a mobile telephone. That is, for example, a radio wave absorption sheet having a radio wave absorption characteristic at 700 to 900 MHz is used for the 800 MHz band, and a radio wave absorption sheet having a radio wave absorption characteristic at 1.4 to 1.65 GHz for the 1.5 GHz band. Use a radio wave absorption sheet having radio wave absorption characteristics at 1.75 to 2.0 GHz for the 1.9 GHz band, and radio wave absorption characteristics at 2.35 to 2.65 GHz for the 2.5 GHz band. The radio wave absorption sheet having

JP-A-10-93286

  By the way, in the radio wave anechoic box according to Patent Document 1, the measurable frequency band is limited to the band that can be absorbed by the radio wave absorbing sheet. For this reason, for example, when evaluating the characteristics of a mobile phone antenna having a wide frequency band that can radiate electromagnetic waves of a plurality of frequency bands, a plurality of radio wave anechoic boxes with different radio wave absorption sheets are prepared. It is necessary to measure in an anechoic box. As a result, there are problems that the measurement time becomes long and a large space is required to place a plurality of radio anechoic boxes. On the other hand, when a radio wave absorber capable of absorbing broadband electromagnetic waves is used, the radio wave absorber becomes large, and the radio wave anechoic box is also enlarged.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a radio anechoic box capable of measuring characteristics of an object to be measured that emits electromagnetic waves in a plurality of frequency bands. It is in.

  In order to solve the above-described problem, a radio wave anechoic box according to the invention of claim 1 includes a metal casing formed in a cylindrical shape whose both ends in the axial direction are closed, and one end face in the axial direction of the metal casing. A first end face side wave absorber that absorbs electromagnetic waves in the first frequency band, and a second end face side electromagnetic wave absorber that absorbs electromagnetic waves in the second frequency band provided on the other end face in the axial direction of the metal casing. An end surface side electromagnetic wave absorber, a first inner peripheral surface side electromagnetic wave absorber that is provided on the inner peripheral surface of the metal casing and absorbs electromagnetic waves in the first frequency band, and is located inside the metal casing. A cylindrical member provided so as to be movable in the axial direction; a second inner peripheral surface-side wave absorber provided on an inner peripheral surface of the cylindrical member for absorbing electromagnetic waves in a second frequency band; and the metal casing. It is located between the first and second end face side wave absorbers inside the body and is provided so as to be movable in the axial direction through the cylindrical member. A flat partition member, a first partition-side radio wave absorber that is provided on a surface of the partition member facing the first end-surface-side radio wave absorber and absorbs electromagnetic waves in a first frequency band, and the partition The member includes a second partition side radio wave absorber that is provided on a surface of the member that faces the second end face side radio wave absorber and absorbs electromagnetic waves in the second frequency band.

  According to a second aspect of the present invention, the metal casing is provided with an object fixing jig for supporting the object to be measured and an antenna mounting jig for supporting the antenna for measurement, and the characteristics of the first frequency band are obtained. When measuring, the cylindrical member is disposed on the end side in the axial direction of the metal casing, the partition member is disposed on the other end face side in the axial direction of the metal casing, and the workpiece fixing jig and The antenna mounting jig is arranged between the first end face side wave absorber and the first partition side wave absorber at a position avoiding the cylindrical member, and the characteristics of the second frequency band are measured. The cylindrical member is disposed on the center side in the axial direction of the metal casing, the partition member is disposed on one end face side in the axial direction of the metal casing, and the workpiece fixing jig and the antenna are mounted. At the position where the jig sandwiches the cylindrical member, the second end face side electromagnetic wave absorber and the second partition side electric It is configured to be disposed between the absorbent body.

  According to a third aspect of the present invention, the cylindrical member includes a plurality of divided cylinders that can be divided at an intermediate position in the axial direction, and the plurality of divided cylinders measure the characteristics of the first frequency band. When the characteristics of the second frequency band are measured, the metal casings are arranged in contact with each other in the axial center of the metal casing. It is configured.

  According to a fourth aspect of the present invention, the first end surface side radio wave absorber, the first inner peripheral surface side radio wave absorber, and the first partition side radio wave absorber absorb electromagnetic waves in the first frequency band on the high frequency side. The second end face side radio wave absorber, the second inner peripheral side radio wave absorber, and the second partition side radio wave absorber are second low frequency side lower than the first frequency band. It absorbs electromagnetic waves in the frequency band.

  In the invention of claim 5, the first end face side radio wave absorber, the first inner peripheral side radio wave absorber, and the first partition side radio wave absorber are made of pyramidal shapes using carbon-containing radio wave absorbers. Alternatively, the second end face side radio wave absorber, the second inner peripheral side radio wave absorber, and the second partition side radio wave absorber are formed in a flat plate shape using a ferrite material. .

  According to the first aspect of the present invention, the first end face side wave absorber is provided on one end face in the axial direction of the metal casing, and the first inner circumference side wave absorber is provided on the inner peripheral face of the metal casing. In addition to the provision, the first partition side radio wave absorber is provided on the surface facing the first end surface side radio wave absorber on the screen member that is movable in the axial direction. Thereby, for example, by arranging the partition member on the other side in the axial direction of the metal casing, a space for absorbing electromagnetic waves in the first frequency band can be secured inside the metal casing. For this reason, the characteristic with respect to the electromagnetic wave of the 1st frequency band can be measured by using the space in this metal housing.

  In addition, a second inner peripheral surface side wave absorber is provided on the inner peripheral surface of the cylindrical member, and the second partition side radio wave absorber is provided on a surface facing the second end surface side radio wave absorber on the partition member. It was set as the structure which provides. Accordingly, for example, by arranging the partition member on one side in the axial direction of the metal casing, a space for absorbing the electromagnetic wave in the second frequency band can be secured inside the cylindrical member. For this reason, the characteristic with respect to the electromagnetic wave of the 2nd frequency band can be measured by using the space in this cylindrical member.

  As a result, electromagnetic waves in two different frequency bands can be measured within a single anechoic box. For this reason, even when evaluating the characteristics of an object that emits electromagnetic waves in two frequency bands, such as a multi-band mobile phone, the electromagnetic waves in all frequency bands are measured in a single anechoic box. Therefore, it is not necessary to perform measurement using a plurality of anechoic boxes as in the prior art, and the efficiency of measurement work can be increased.

  According to the second aspect of the present invention, the metal casing is provided with the measured object fixing jig for supporting the measured object and the antenna mounting jig for supporting the measurement antenna. For this reason, when measuring the characteristics of the first frequency band, the cylindrical member is disposed on the axial end portion side of the metal casing, and the partition member is disposed on the other end face side in the axial direction of the metal casing. . Accordingly, a space for absorbing electromagnetic waves in the first frequency band can be secured between the first end surface side radio wave absorber and the first partition side radio wave absorber in the axial direction of the metal casing. it can. For this reason, by arranging the measurement object fixing jig and the antenna mounting jig at a position avoiding the cylindrical member, the measurement object fixing jig and the antenna mounting jig can be arranged in this space. The characteristics of the first frequency band can be measured.

  On the other hand, when measuring the characteristics of the second frequency band, the cylindrical member is disposed on the center side in the axial direction of the metal casing, and the partition member is disposed on one end face side in the axial direction of the metal casing. As a result, the electromagnetic wave in the second frequency band is located between the second end face side wave absorber and the second partition side wave absorber in the axial direction of the metal casing located inside the cylindrical member. It is possible to secure a space to absorb For this reason, by placing the measured object fixing jig and the antenna mounting jig at a position sandwiching the cylindrical member, the measured object fixing jig and the antenna mounting jig can be disposed in this space. The characteristic of the second frequency band can be measured.

  According to invention of Claim 3, the cylindrical member was comprised with the some division | segmentation cylinder body which can be divided | segmented in the axial direction middle position. For this reason, when measuring the characteristics of the first frequency band, the plurality of divided cylinders can be arranged in a state of being separated from each other at both axial ends of the metal casing. On the other hand, when measuring the characteristics of the second frequency band, they can be arranged in the state of abutting each other on the axially central side of the metal casing.

  According to the invention of claim 4, the first end surface side radio wave absorber, the first inner peripheral surface side radio wave absorber and the first partition side radio wave absorber absorb electromagnetic waves in the first frequency band on the high frequency side. The second end surface side radio wave absorber, the second inner circumferential surface side radio wave absorber, and the second partition side radio wave absorber absorb the electromagnetic waves in the second frequency band on the low frequency side. It was. Here, a radio wave absorber that absorbs electromagnetic waves on the high frequency side is generally formed in a pyramid shape and has a large protruding dimension. For this reason, for example, when the second inner circumferential surface side radio wave absorber located on the inner circumferential side of the tubular member absorbs electromagnetic waves on the high frequency side, the radio wave absorber, the antenna for measurement, and the object to be measured A sufficient distance cannot be secured, and coupling occurs between the radio wave absorber and the measurement antenna or the like, resulting in a problem that the measurement accuracy of the electromagnetic wave is lowered. In addition, when a sufficient distance between the radio wave absorber and the measurement antenna is secured, the entire radio anechoic box becomes large.

  On the other hand, in the present invention, since the first inner peripheral surface side radio wave absorber is configured to absorb electromagnetic waves in the first frequency band on the high frequency side, the first inner peripheral surface side radio wave absorber is cylindrical. The distance from the measurement antenna or the like can be increased compared to the inside of the member. For this reason, the coupling between the radio wave absorber and the measurement antenna and the like can be reduced, the electromagnetic wave measurement accuracy can be increased, and the entire radio anechoic box can be miniaturized.

  According to the invention of claim 5, the first end face side radio wave absorber, the first inner peripheral side radio wave absorber, and the first partition side radio wave absorber are made of carbon-containing radio wave absorbers and pyramids. Since it is formed in a shape or a taper shape, an electromagnetic wave on the high frequency side can be absorbed using a wave absorber such as a pyramid shape.

  On the other hand, since the second end surface side wave absorber, the second inner peripheral surface side wave absorber and the second partition side wave absorber are formed in a flat plate shape using a ferrite material, the ferrite material wave absorber Can be used to absorb electromagnetic waves on the low frequency side. In addition, since the second inner peripheral surface side wave absorber and the like are formed in a flat plate shape using a ferrite material, the projecting dimension of the wave absorber can be reduced, and a large measurement space is provided inside the cylindrical member or the like. Can be secured.

  Hereinafter, an anechoic box according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  1 to 14, a radio anechoic box 1 includes a metal casing 2 formed in a box shape using an aluminum plate having a thickness of, for example, about 1 to 2 mm, and the metal casing 2 It is comprised by the electromagnetic wave absorber 3 provided in the inside. The radio wave anechoic box 1 blocks external electromagnetic waves and prevents reflection of internal electromagnetic waves.

  Here, the metal housing 2 is formed with a length dimension of about 50 to 100 cm, for example, with respect to the width direction (X direction), the axial direction (Y direction), and the height direction (Z direction). The metal housing 2 includes a front wall surface 2A and a rear wall surface 2B located on both sides in the axial direction, a left wall surface 2C and a right wall surface 2D located on both sides in the width direction, a ceiling surface 2E located on both sides in the height direction, and a bottom surface. 2F. At this time, the front and rear wall surfaces 2A and 2B form opposing surfaces facing each other. The left and right wall surfaces 2C and 2D also form opposed surfaces that face each other, and the ceiling surface 2E and the bottom surface 2F also form opposed surfaces that face each other.

  The left and right wall surfaces 2C and 2D, the ceiling surface 2E, and the bottom surface 2F extend in the axial direction to form a rectangular cylinder, and both end sides in the axial direction are closed by the front wall surface 2A and the rear wall surface 2B. A door 2G is attached to the right wall surface 2D so as to be openable and closable in order to mount an object to be measured 17 described later in the metal casing 2.

  As shown in FIGS. 2 to 5, the first end surface side radio wave absorber 3 is provided, for example, on the front wall surface 2 </ b> A among the front wall surface 2 </ b> A and the rear wall surface 2 </ b> B located on both sides in the axial direction of the metal casing 2. It covers substantially the entire front wall surface 2A. Further, the end surface side radio wave absorber 3 is formed in a pyramid shape or a taper shape having a projecting dimension of about 10 to 15 cm using a radio wave absorber material such as a urethane material containing carbon. Protrusively toward. The end-surface-side radio wave absorber 3 has high absorption characteristics for electromagnetic waves in the frequency band on the high frequency side and absorbs electromagnetic waves in the frequency band on the low frequency side when the DUT 17 radiates electromagnetic waves in the two frequency bands. The structure has low characteristics. More specifically, for example, when a cellular phone capable of emitting electromagnetic waves in two frequency bands of 800 MHz band and 1.9 GHz band is used as the object to be measured 17, the end surface side radio wave absorber 3 has a frequency of 1.9 GHz band or higher. The electromagnetic wave in the frequency band has high absorption characteristics, and the electromagnetic wave in the frequency band lower than the 1.9 GHz band has low absorption characteristics. For this reason, the end surface side radio wave absorber 3 has an absorption characteristic higher than, for example, −20 dB for electromagnetic waves in the 1.9 GHz band or higher, and an absorption characteristic lower than −20 dB for electromagnetic waves in a frequency band lower than the 1.9 GHz band. It has composition which has.

  The second end face side wave absorber 4 is the front wall face 2A provided with the first end face side wave absorber 3 of the front wall face 2A and the rear wall face 2B located on both axial sides of the metal housing 2. It is provided on a different rear wall surface 2B and covers substantially the entire rear wall surface 2B. Moreover, the end surface side electromagnetic wave absorber 4 is formed in a flat plate shape using, for example, a ferrite material as a material that absorbs electromagnetic waves. The end-surface-side radio wave absorber 4 has high absorption characteristics for electromagnetic waves in the frequency band on the low frequency side and absorbs electromagnetic waves in the frequency band on the high frequency side when the DUT 17 radiates electromagnetic waves in the two frequency bands. The structure has low characteristics. For this reason, the end surface side radio wave absorber 4 has an absorption characteristic higher than −20 dB for electromagnetic waves in a frequency band of, for example, 800 MHz or less, and an absorption characteristic lower than −20 dB for electromagnetic waves in a frequency band higher than the 800 MHz band. It is the composition which has.

  The first inner peripheral surface side wave absorber 5 is provided on the left wall surface 2C, the right wall surface 2D, the ceiling surface 2E, and the bottom surface 2F, which are the inner peripheral surface of the metal casing 2, and covers substantially the entire surface thereof. Further, the inner peripheral surface side radio wave absorber 5 is formed in a pyramid shape or the like using a radio wave absorbing material containing carbon in substantially the same manner as the end surface side radio wave absorber 3. The inner peripheral surface side electromagnetic wave absorber 5 has a high absorption characteristic in the electromagnetic wave in the frequency band on the high frequency side (1.9 GHz band or higher), and the electromagnetic wave in the frequency band on the low frequency side (lower than the 1.9 GHz band). Absorption characteristics are low.

  The holding cylinder 6 is provided inside the metal housing 2 so as to be movable in the axial direction. Further, the holding cylinder 6 is formed in, for example, a substantially rectangular cylinder, and both end sides in the axial direction are open. Furthermore, the holding cylinder 6 has a left wall surface 6A and a right wall surface 6B located on both sides in the width direction, and a ceiling surface 6C and a bottom surface 6D located on both sides in the height direction. And the holding cylinder 6 accommodates the partition member 12 in the inside, when the partition member 12 mentioned later is arrange | positioned at the front wall surface 2A side of the metal housing | casing 2. As shown in FIG.

  The cylindrical member 7 is provided inside the metal housing 2 so as to be movable in the axial direction. Moreover, the cylindrical member 7 is comprised by the 1st, 2nd division | segmentation cylinders 8 and 9 which can be divided | segmented in the axial middle position. Here, the divided cylindrical bodies 8 and 9 are formed in, for example, a substantially rectangular cylindrical shape, and both end sides in the axial direction are open. The divided cylinders 8 and 9 have left wall surfaces 8A and 9A and right wall surfaces 8B and 9B located on both sides in the width direction, and ceiling surfaces 8C and 9C and bottom surfaces 8D and 9D located on both sides in the height direction. ing. The divided cylinders 8 and 9 are substantially the same size and the same shape as the holding cylinder 6, but the axial length is larger than that of the holding cylinder 6.

  Further, the bottom surfaces 6D, 8D, and 9D of the holding cylinder 6 and the divided cylinders 8 and 9 are positioned between the bottom surface 2F of the metal housing 2 and move the cylinders 6, 8, and 9 in the axial direction. A moving mechanism 10 is provided. At this time, the moving mechanism 10 is provided on the two rails 10A provided on the bottom surface 2F of the metal casing 2 and the bottom surfaces 6D, 8D, and 9D of the cylinders 6, 8, and 9 along the rail 10A. It is comprised by the wheel 10B which moves. Further, the rail 10 </ b> A extends linearly along the axial direction of the metal housing 2. On the other hand, the wheel 10B advances in the axial direction along the rail 10A while being supported by the rail 10A. For this reason, the cylinders 6, 8, and 9 are configured to smoothly move in the axial direction by the moving mechanism 10.

  When measuring the characteristics of the frequency band on the high frequency side (1.9 GHz band or higher), the holding cylinder 6 and the first divided cylinder 8 are arranged on the front wall surface 2A side of the metal housing 2, for example. On the other hand, the second divided cylindrical body 9 is disposed, for example, on the rear wall 2B side of the metal housing 2 in order to hold a partition member 12 described later in a state of covering the second end surface side wave absorber 4. . At this time, the partition member 12 is accommodated in the second divided cylindrical body 9. Thereby, the division cylinders 8 and 9 are arrange | positioned in the state isolate | separated from the axial direction both ends of the metal housing | casing 2 mutually.

  On the other hand, when measuring the characteristics of the frequency band on the low frequency side (800 MHz band or higher), the holding cylinder 6 holds the partition member 12 described later in a state of covering the first end face side radio wave absorber 3. For example, it arrange | positions at the front wall surface 2A side of the metal housing | casing 2. FIG. At this time, the partition member 12 is accommodated in the holding cylinder 6. Further, the first and second divided cylindrical bodies 8 and 9 are located on the axially central side of the metal housing 2 and are arranged in contact with each other.

  The second inner peripheral surface side radio wave absorber 11 is provided on the inner peripheral surface of each of the cylinders 6, 8, 9 and covers substantially the entire surface thereof. For this reason, the inner peripheral surface side electromagnetic wave absorber 11 includes the left wall surfaces 6A, 8A, 9A, the right wall surfaces 6B, 8B, 9B, the ceiling surfaces 6C, 8C, 9C and the bottom surfaces 6D, 8D of the divided cylinders 6, 8, 9. , 9D. Further, the inner peripheral surface side wave absorber 11 is formed in a flat plate shape using a ferrite material in substantially the same manner as the end surface side wave absorber 4. The inner peripheral surface side electromagnetic wave absorber 11 has high absorption characteristics for electromagnetic waves in the frequency band on the low frequency side (800 MHz band or lower), and low absorption characteristics for electromagnetic waves in the frequency band on the high frequency side (higher than 800 MHz band). It has become.

  The partition member 12 is formed in a flat plate shape having a plane (XZ plane) orthogonal to the axial direction, and is located inside the metal housing 2 and is located in the first and second end face side wave absorbers 3 with respect to the axial direction. , 4 are arranged. The partition member 12 has an area smaller than the opening area of the tubular member 7 so as to close the opening of the tubular member 7 and is provided so as to be movable in the axial direction through the inside of the tubular member 7. ing.

  Furthermore, a moving mechanism 13 is provided at the bottom of the partition member 12 to move the partition member 12 in the axial direction, located between the bottom surfaces 6D, 8D, and 9D of the cylinders 6, 8, and 9. Yes. At this time, the moving mechanism 13 is located inside the cylinders 6, 8, 9, two rails 13 </ b> A provided on the bottom surfaces 6 </ b> D, 8 </ b> D, 9 </ b> D, and the rail 13 </ b> A provided at the bottom of the partition member 12. And a wheel 13 </ b> B that moves along the wheel. Further, although the rail 13A is divided into the cylinders 6, 8, and 9, they are connected to each other when the divided cylinders 6, 8, and 9 are connected, and are linear along the axial direction of the metal housing 2. It is the structure extended to. On the other hand, the wheel 13B advances in the axial direction along the rail 13A while being supported by the rail 13A. For this reason, the partition member 12 is configured to smoothly move the inside of the cylindrical member 7 in the axial direction by the moving mechanism 13.

  The first partition side radio wave absorber 14 is provided on the front surface of the partition member 12 facing the first end surface side radio wave absorber 3. The partition-side radio wave absorber 14 is formed in a pyramid shape or the like using a radio wave absorbing material containing carbon in substantially the same manner as the end-surface-side radio wave absorber 3, and covers the rear surface of the partition member 12 over substantially the entire surface. Yes. The partition-side radio wave absorber 14 has high absorption characteristics for electromagnetic waves in the frequency band on the high frequency side (1.9 GHz band or higher), and has absorption characteristics for electromagnetic waves in the frequency band on the low frequency side (lower than the 1.9 GHz band). Is low.

  Furthermore, the partition-side radio wave absorber 14 moves in the axial direction together with the partition member 12 and faces the end-surface-side radio wave absorber 3 in a state of being close when the partition member 12 is disposed on the front wall surface 2A side. . At this time, the partitioning-side radio wave absorber 14 is in the Z direction and the X direction so that the protruding end portion (the apex portion of the pyramid shape) does not contact (interfere) with the protruding end portion of the end surface side radio wave absorber 3. They are staggered. Thereby, when the end surface side radio wave absorber 3 and the partition side radio wave absorber 14 overlap each other in the axial direction, the total axial dimension of the radio wave absorbers 3 and 14 can be reduced. As a result, the partition member 12 does not enter the metal housing 2 more than necessary, so that interference between the partition member 12 and the measurement antenna 19 can be prevented and the axial dimension of the metal housing 2 can be prevented. Can be reduced.

  The second partition side radio wave absorber 15 is provided on the rear surface of the partition member 12 facing the second end surface side radio wave absorber 4. The partition-side radio wave absorber 15 is formed in a flat plate shape using a ferrite material in substantially the same manner as the end-surface-side radio wave absorber 4 and covers the rear surface of the partition member 12 over substantially the entire surface. The partition-side radio wave absorber 15 has high absorption characteristics for electromagnetic waves in the frequency band on the low frequency side (800 MHz band or lower), and has low absorption characteristics for electromagnetic waves in the frequency band on the high frequency side (higher than 800 MHz band). Yes.

  The measurement object fixing jig 16 is provided on the rear wall surface 2 </ b> B side of the metal housing 2. Further, the measurement object fixing jig 16 is attached in a state of hanging from the ceiling surface 2E of the metal casing 2, and a fixed base 16A for attaching the measurement object 17 is provided at the tip thereof. And the to-be-measured object fixing jig 16 is provided with a rotating mechanism (not shown) that rotates in a biaxial direction, for example, and constitutes a biaxial positioner. Therefore, the object fixing jig 16 rotates the object 17 in the azimuth angle θ direction around the O1 axis parallel to the height direction (Z direction) and O2 parallel to the axial direction (Y direction). It is configured to rotate around the axis in the elevation angle φ direction.

  Further, the DUT 16 is attached so as to be displaceable in the height direction, and is configured to be able to advance and retreat in the metal housing 2. For this reason, the workpiece fixing jig 16 is retracted from the metal housing 2 when the cylindrical member 7 and the partition member 12 are moved in the axial direction, and when measuring the electromagnetic wave characteristics of the workpiece 17 Enter the case 2.

  The object to be measured 17 is attached to a fixed base 16A of the object to be measured fixing jig 16, and rotates around two axes of the O1 axis and the O2 axis as shown in FIGS. In addition, the device under test 17 includes, for example, a mobile phone, a mobile terminal, and the like, and includes a device under test 17A as a measurement target for measuring the radiation efficiency. At this time, the antenna 17A to be measured is constituted by, for example, a whip antenna, a built-in chip antenna, or the like. Further, for example, a cellular phone that can radiate electromagnetic waves of a plurality of frequency bands such as 800 MHz band and 1.9 GHz band is applied to the object to be measured 17. In addition, although the to-be-measured object 17 illustrated as what radiates | emits electromagnetic waves of two frequency bands, it is good also as a structure which radiates | emits electromagnetic waves of two or more frequency bands.

  The antenna mounting jig 18 is provided on the front wall surface 2A side of the metal housing 2 as shown in FIGS. The antenna mounting jig 18 is mounted in a state where it is suspended from the ceiling surface 2E of the metal casing 2 in the same manner as the measured object fixing jig 16, and a measurement antenna 19 described later is mounted on the tip thereof. The antenna mounting jig 18 is configured to switch the polarization (horizontal polarization, vertical polarization) measured by the measurement antenna 19.

  The antenna mounting jig 18 is mounted so as to be displaceable in the height direction and is configured to be able to advance and retreat in the metal housing 2, similarly to the measurement object fixing jig 16. For this reason, the antenna mounting jig 18 moves out of the metal casing 2 when moving the cylindrical member 7 and the partition member 12 in the axial direction, and when measuring the electromagnetic wave characteristics of the object 17 to be measured, Enter 2

  The measurement antenna 19 is provided inside the metal housing 2, for example, on the front wall surface 2 </ b> A side in the axial direction. Further, the measurement antenna 19 is attached to the tip end side of the antenna attachment jig 18 and is disposed in a state of being opposed to a position separated from the DUT 17 by a predetermined distance dimension in the axial direction (Y direction). Here, the measurement antenna 19 is constituted by a small biconical antenna, for example, and selectively measures one of horizontal polarization and vertical polarization. The measurement antenna 19 is connected to a network analyzer 20 described later.

  The network analyzer 20 constitutes an electromagnetic field measuring device that measures the electromagnetic field radiated by the device under test 17 (measured antenna 17A), and is connected to the measured antenna 17A through the high frequency cable 20A and measured through the high frequency cable 20B. It is connected to the antenna 19 for use. The network analyzer 20 receives the electromagnetic wave (high-frequency signal) transmitted from the antenna to be measured 17 </ b> A using the measurement antenna 19. As a result, the network analyzer 20 calculates the ratio between the power supplied to the antenna to be measured 17A and the power received from the measurement antenna 19, and measures the parameter S21 of the S matrix corresponding to the space loss.

  The radio wave anechoic box 1 according to the present embodiment is configured as described above. Next, the frequency bands of electromagnetic waves to be measured using the measurement antenna 19 are set to the high frequency side (1.9 GHz band) and the low frequency side. A method of switching the measurement frequency band that is switched between (800 MHz band) will be described.

  First, the radio anechoic box 1 will be described with respect to a configuration for measuring electromagnetic waves in a frequency band on the high frequency side (1.9 GHz band). In this case, as shown in FIG. 2, the divided cylindrical bodies 8 and 9 of the cylindrical member 7 are arranged separately on both ends in the axial direction of the metal housing 2, and the partition member 12 is accommodated inside the divided cylindrical body 9. In this state, the metal housing 2 is disposed on the rear wall 2B side. Further, the measurement object fixing jig 16 and the antenna mounting jig 18 are arranged between the divided cylinders 8 and 9 spaced apart from each other in the axial direction so as to avoid the divided cylinders 8 and 9, and the first end surface side radio wave It arrange | positions between the absorber 3 and the 1st screen side electromagnetic wave absorber 14. FIG. As a result, the DUT 17 and the measurement antenna 19 are surrounded by the first inner circumferential surface side wave absorber 5, and both sides in the axial direction are sandwiched between the wave absorbers 3 and 14. For this reason, the primary reflection surface between the DUT 17 and the measurement antenna 19 is covered with the radio wave absorbers 3, 5, and 14 that absorb electromagnetic waves in the high frequency band.

  Next, a procedure for switching the high frequency radio wave absorbers 3, 5, and 14 (the state of FIG. 2) to the low frequency radio wave absorbers 4, 11, and 15 (the state of FIG. 3) will be described with reference to FIGS. This will be described with reference to FIG.

  First, the door 2G of the metal housing 2 is opened, the measurement object 17 is removed from the measurement object fixing jig 16, and the measurement antenna 19 is removed from the antenna attachment jig 18. Thereafter, as shown in FIG. 7, the workpiece fixing jig 16 and the antenna mounting jig 18 are pulled up, and these are retracted from the metal housing 2. Thereby, the cylindrical member 7 and the partition member 12 will be in the state which can move to an axial direction.

  Next, as shown in FIG. 8, the split cylinder 9 is moved in the axial direction from the rear wall surface 2B side toward the front wall surface 2A side. At this time, the partition member 12 is accommodated in the divided cylindrical body 9. For this reason, the partition member 12 also moves in the axial direction toward the front wall surface 2 </ b> A together with the divided cylindrical body 9.

  Then, the divided cylinder 9 that has moved to the front wall surface 2 </ b> A abuts on the end of the divided cylinder 8 and is connected to the cylinders 6 and 8. Thereby, the rail 13A of the moving mechanism 13 is connected on the bottom surfaces 6D, 8D, and 9D of the cylinders 6, 8, and 9.

  Next, as the wheel 13B moves along the rail 13A, the partition member 12 moves from the divided cylinder 9 into the holding cylinder 6 as shown in FIG. Thereby, the 1st partition side electromagnetic wave absorber 14 approaches the 1st end surface side electromagnetic wave absorber 3 provided in 2 A of front wall surfaces, and is arrange | positioned in the state which mutually overlapped. On the other hand, the second partition side radio wave absorber 15 is located on the front wall surface 2A side, while the second end surface side radio wave absorber 4 is provided on the rear wall surface 2B. For this reason, the radio wave absorbers 4 and 15 are disposed on both ends in the axial direction of the metal casing 2.

  Next, as shown in FIG. 10, the workpiece fixing jig 16 is pulled down to enter the inside of the metal housing 2. In this state, the divided cylinders 8 and 9 of the cylindrical member 7 are moved to the center side in the axial direction of the metal housing 2. At this time, the partition member 12 is held on the front wall surface 2 </ b> A side of the metal housing 2 together with the holding cylinder 6. Moreover, since the end surfaces of the divided cylinders 8 and 9 are in contact with each other, the divided cylinders 8 and 9 are connected to each other. The fixed base 16 </ b> A of the measurement object fixing jig 16 is disposed inside the divided cylindrical body 9.

  Next, the antenna mounting jig 18 is pulled down to enter the inside of the metal housing 2. As a result, the divided cylinders 8 and 9 (tubular member 7) are disposed between the DUT 16 and the antenna mounting jig 18.

  Finally, as shown in FIG. 3, the measurement object 17 is attached to the fixed base 16 </ b> A of the measurement object fixing jig 16, and the measurement antenna 19 is attached to the antenna attachment jig 18. Thereby, the cylindrical member 7 is arrange | positioned at the axial direction center side of the metal housing | casing 2, and the partition member 12 is in the state which was accommodated in the inside of the holding | maintenance cylinder 6, and the axial front wall surface 2A side of the metallic housing 2 Be placed. Further, the DUT 16 and the antenna mounting jig 18 are disposed between the second end face side wave absorber 4 and the second partition side wave absorber 15 with the cylindrical member 7 interposed therebetween. Is done. As a result, the DUT 17 and the measurement antenna 19 are located inside the cylindrical member 7 and are surrounded by the second inner peripheral surface side wave absorber 11 and are also axially moved by the wave absorbers 4 and 15. Both sides are sandwiched. For this reason, the primary reflection surface between the DUT 17 and the measurement antenna 19 is covered with the radio wave absorbers 4, 11, 15 that absorb electromagnetic waves in the low frequency band.

  Next, contrary to the above, the procedure for switching the low-frequency wave absorbers 4, 11, and 15 (state of FIG. 3) to the high-frequency wave absorbers 3, 5, and 14 (state of FIG. 2), This will be described with reference to FIGS.

  First, the door 2G of the metal housing 2 is opened, the measurement object 17 is removed from the measurement object fixing jig 16, and the measurement antenna 19 is removed from the antenna attachment jig 18. Thereafter, as shown in FIG. 11, the antenna mounting jig 18 is pulled up and retracted from the metal housing 2. Thereby, the cylindrical member 7 will be in the state which can move toward the front wall surface 2A side in an axial direction. Therefore, the cylindrical member 7 is moved to the front wall surface 2 </ b> A side until it comes into contact with the holding cylinder 6. At this time, the holding cylinder 6 abuts on the end of the divided cylinder 8 and is connected to the divided cylinders 8 and 9. For this reason, the rail 13A of the moving mechanism 13 is connected on the bottom surfaces 6D, 8D, and 9D of the cylinders 6, 8, and 9. And after the cylindrical member 7 moves, the to-be-measured object fixing jig 16 is pulled up and retracted from the inside of the metal housing 2.

  Next, as shown in FIG. 12, the holding cylinder 6 is moved together with the cylindrical member 7 in the axial direction from the front wall surface 2A side to the rear wall surface 2B side. At this time, the partition member 12 is accommodated in the holding cylinder 6. For this reason, the partition member 12 also moves in the axial direction toward the rear wall surface 2 </ b> B together with the holding cylinder 6. Then, in a state where the cylinders 6, 8, and 9 are connected, the cylinders 6, 8, and 9 are moved to the rear wall 2B side until the divided cylinder 9 comes into contact (abutment) with the rear wall 2B.

  Next, as the wheel 13B moves along the rail 13A, the partition member 12 moves from the holding cylinder 6 into the divided cylinder 9 as shown in FIG. Thereby, the 2nd partition side electromagnetic wave absorber 15 approaches the 2nd end surface side electromagnetic wave absorber 4 provided in the rear wall surface 2B, and is arrange | positioned in the state which mutually overlapped. On the other hand, the first partition side radio wave absorber 14 is located on the rear wall surface 2B side, while the first end surface side radio wave absorber 3 is provided on the front wall surface 2A. For this reason, the radio wave absorbers 3 and 14 are disposed on both ends of the metal housing 2 in the axial direction.

  Next, as shown in FIG. 14, the holding cylinder 6 and the divided cylinder 8 are moved to the front wall surface 2A side. Thereby, a space in which the first inner peripheral surface side wave absorber 5 is exposed is defined between the divided cylindrical bodies 8 and 9.

  Next, the workpiece fixing jig 16 and the antenna mounting jig 18 are pulled down to enter the inside of the metal housing 2. At this time, the DUT 16 and the antenna mounting jig 18 are disposed between the divided cylinders 8 and 9 with respect to the axial direction as positions avoiding the divided cylinders 8 and 9.

  Finally, as shown in FIG. 2, the measurement object 17 is attached to the fixed base 16 </ b> A of the measurement object fixing jig 16, and the measurement antenna 19 is attached to the antenna mounting jig 18. Thereby, the divided cylinders 8 and 9 are arranged separately on both ends in the axial direction of the metal casing 2, and the partition wall 12 is accommodated inside the divided cylinder 9 and the rear wall surface 2 </ b> B of the metal casing 2. Placed on the side. The object fixing jig 16 and the antenna mounting jig 18 are located between the divided cylindrical bodies 8 and 9 spaced apart in the axial direction, and the first end face side radio wave absorber 3 and the first partition side radio wave. It arrange | positions between the absorbers 14. As a result, the primary reflection surface between the DUT 17 and the measurement antenna 19 is covered with the radio wave absorbers 3, 5, and 14 that absorb electromagnetic waves in the high frequency band.

  The radio anechoic box 1 according to the present embodiment is configured as described above. Next, a method for measuring antenna characteristics (antenna radiation efficiency) using the radio anechoic box 1 will be described.

  First, as shown in FIG. 2, the inside of the metal housing 2 is in a state in which, for example, radio wave absorbers 3, 5, and 14 for high frequency are exposed. In this state, the measurement object 17 is attached to the measurement object fixing jig 16. At this time, the DUT 17 is installed in a horizontal state. Before starting the measurement, the network analyzer 20 directly connects the high-frequency cable 20A connected to the device under test 17 and the high-frequency cable 20B connected to the measurement antenna 19, and is calibrated by the loss due to the high-frequency cables 20A and 20B. Correct (calibration).

  Next, using the measurement object fixing jig 16, the posture of the measurement object 17 is fixed at a position where the azimuth angle θ and the elevation angle φ are both 0 °. In this state, the network analyzer 20 is used to radiate electromagnetic waves in the frequency band (1.9 GHz band) on the high frequency side from the device under test 17 (measuring antenna 17A), and to measure the radiated horizontally polarized waves to the measuring antenna 19. The parameter S21 (R0, 0 °, 0 °) at this time is measured. When the measurement of the parameter S21 (R0, θ, φ) is completed in one posture of the device under test 17, the azimuth angle θ of the device under test 17 is increased by 10 ° using the device under test fixture 16. The parameter S21 (R0, 10 °, 0 °) is measured again. This operation is repeated when the azimuth angle θ is in the range of 0 ° to 360 °.

  Then, after rotating the device under test 17 by one turn in the azimuth angle θ direction, the network analyzer 20 is used to measure the vertical polarization radiated from the device under test 17 (measuring antenna 17A). 19 to receive. At this time, the antenna mounting jig 18 is used to switch the polarization measured by the measurement antenna 19 from horizontal polarization to vertical polarization. In this state, as in the case of the horizontal polarization described above, the device under test 17 is rotated in the azimuth angle θ direction with the elevation angle φ of the device under test 17 fixed at 0 ° again. Thus, the parameter S21 (R, θ, 0 °) in the azimuth angle θ direction is measured every 10 °, for example, in the range of the azimuth angle θ of 0 ° to 360 °.

  After the measurement is completed when the elevation angle φ is fixed at 0 °, the elevation angle φ of the measurement object 17 is increased by 10 ° using the measurement object fixing jig 16. In this state, the azimuth angle θ is changed again every 10 ° in the range of 0 ° to 360 °, and the parameter S21 (R, θ, 10 °) for horizontal polarization and vertical polarization is measured. The above operation is repeated for the azimuth angle θ in the range of 0 ° to 360 ° and the elevation angle φ in the range of 0 ° to 180 °, and the parameter S21 (R, θ, φ) at each azimuth angle θ and elevation angle φ is measured. To do.

When the measurement for all the azimuth angles θ and elevation angles φ is completed, the square polarization S21 ² (R, θ, φ) of the horizontal polarization measurement results and the measurement results of vertical polarization for each azimuth angle θ and elevation angle φ. square S21 ² of (R, theta, phi) adds the squared S21 ² final parameter S21 (R, θ, φ) is calculated. At this time, the measurement result of the horizontal polarization and the measurement result of the vertical polarization are added not by the logarithmic display (dB) measured by the network analyzer 20 but by a numerical value converted to a true number.

  Finally, the parameter S21 (R, θ, φ) based on the measurement result of the horizontal polarization and the measurement result of the vertical polarization is spherically integrated over the entire space, and the radiation efficiency η of the DUT 17 (the antenna to be measured) 17A antenna characteristics) is calculated based on the following equation (1).

  In Equation 1, λ 0 represents the wavelength of the measurement frequency, and G represents the gain of the measurement antenna 19. Further, Δφ represents a measurement angle step in the elevation angle φ direction. In the present embodiment, Δφ is 10 ° (Δφ = π / 18 [radian]). Further, Δθ indicates a measurement angle step in the azimuth angle θ direction. In the present embodiment, for example, Δθ is 10 ° (Δθ = π / 18 [radian]).

  Then, after the measurement of the frequency band on the high frequency side (1.9 GHz band) for the DUT 17 is completed, as shown in FIG. Are switched to the low-frequency wave absorbers 4, 11, 15. In this state, the measurement procedure described above is repeated to measure the low frequency side frequency band (800 MHz band) of the DUT 17. As a result, two frequency bands can be measured using the single anechoic box 1.

  Thus, in the present embodiment, the first end surface side radio wave absorber 3 is provided on the axial front wall surface 2 </ b> A of the metal casing 2, and the first inner peripheral surface side radio wave absorption is provided on the inner peripheral surface of the metal casing 2. In addition to providing the body 5, the partition member 12 movable in the axial direction has a configuration in which the first partition side radio wave absorber 14 is provided on the front surface facing the first end surface side radio wave absorber 3. Thereby, for example, by arranging the partition member 12 on the rear wall surface 2B side in the axial direction of the metal casing 2, electromagnetic waves in the frequency band (1.9 GHz band) on the high frequency side are absorbed inside the metal casing 2. Space can be secured. For this reason, the characteristic with respect to the electromagnetic wave of the frequency band of a high frequency side can be measured by using the space in this metal housing | casing 2. FIG.

  A second inner peripheral surface side wave absorber 11 is provided on the inner peripheral surface of the cylindrical member 7, and a second partition is provided on the rear surface of the partition member 12 that faces the second end surface side radio wave absorber 4. The side radio wave absorber 15 is provided. Thereby, for example, by arranging the partition member 12 on the side of the front wall surface 2 </ b> A in the axial direction of the metal housing 2, a space that absorbs electromagnetic waves in the low frequency side frequency band (800 MHz band) inside the cylindrical member 7. Can be secured. For this reason, the characteristic with respect to the electromagnetic wave of the frequency band of a low frequency side can be measured by using the space in this cylindrical member 7. FIG.

  As a result, electromagnetic waves in two different frequency bands can be measured in the single anechoic box 1. For this reason, even when evaluating the characteristics of the object to be measured 17 that radiates electromagnetic waves of two frequency bands, such as a multi-band mobile phone, the electromagnetic waves of all frequency bands within the single anechoic box 1. It is not necessary to measure using a plurality of radio anechoic boxes as in the prior art, and the efficiency of measurement work can be increased.

  Further, the metal casing 2 is provided with a device fixing jig 16 that supports the device 17 to be measured and an antenna mounting jig 18 that supports the measurement antenna 19. For this reason, when measuring the characteristics of the frequency band on the high frequency side, the cylindrical member 7 is disposed on both ends in the axial direction of the metal casing 2, and the partition member 12 is disposed on the rear wall 2 </ b> B side in the axial direction of the metal casing 2. To place. Thus, a space for absorbing electromagnetic waves in the frequency band on the high frequency side is secured between the first end surface side wave absorber 3 and the first partition side wave absorber 14 in the axial direction of the metal housing 2. can do. For this reason, the characteristics of the frequency band on the high frequency side can be measured by disposing the DUT 16 and the antenna mounting jig 18 in this space.

  On the other hand, when measuring the characteristics of the frequency band on the low frequency side, the cylindrical member 7 is disposed on the center side in the axial direction of the metal housing 2, and the partition member 12 is disposed on the front wall surface 2 </ b> A side in the axial direction of the metal housing 2. To place. Thereby, the low frequency side is located between the second end face side wave absorber 4 and the second partition side wave absorber 15 in the axial direction of the metal housing 2 located inside the cylindrical member 7. A space for absorbing electromagnetic waves in the frequency band can be secured. For this reason, the characteristics of the frequency band on the low frequency side can be measured by disposing the DUT 16 and the antenna mounting jig 18 on both ends of the cylindrical member 7 in the axial direction.

  Moreover, the cylindrical member 7 was comprised by the two division | segmentation cylinders 8 and 9 which can be divided | segmented in the axial middle position. For this reason, when measuring the characteristics of the frequency band on the high frequency side, the divided cylindrical bodies 8 and 9 can be arranged in a state of being separated from each other at both axial ends of the metal housing 2. On the other hand, when measuring the characteristics of the frequency band on the low frequency side, the metal casing 2 can be disposed in a state of being in contact with each other on the center side in the axial direction.

  Moreover, since the inner peripheral surface side electromagnetic wave absorber 11 that absorbs electromagnetic waves in the frequency band on the high frequency side is formed using a ferrite material, it tends to be relatively heavy and difficult to move. On the other hand, in the present embodiment, since the cylindrical member 7 is divided into the two divided cylinders 8 and 9, the weight of each of the divided cylinders 8 and 9 can be reduced, and the divided cylinder 8 9 can be easily moved.

  Furthermore, the radio wave absorbers 3, 5, and 14 provided in the metal housing 2 and the like are configured to absorb electromagnetic waves in the frequency band on the high frequency side, and the radio wave absorbers 4, 11, and 15 provided in the cylindrical member 7 and the like. Is configured to absorb electromagnetic waves in the frequency band on the low frequency side. Here, a radio wave absorber that absorbs electromagnetic waves on the high frequency side is generally formed in a pyramid shape and has a large protruding dimension. For this reason, for example, when the second inner peripheral surface side radio wave absorber 11 positioned on the inner peripheral side of the cylindrical member 7 absorbs electromagnetic waves on the high frequency side, the radio wave absorber 11 and the measurement antenna 19 are used. Further, there is a problem that a sufficient distance from the object to be measured 17 cannot be secured, coupling occurs between the radio wave absorber 11 and the measurement antenna 19 and the like, and the measurement accuracy of electromagnetic waves is lowered. Further, when a sufficient distance between the radio wave absorber 11 and the measurement antenna 19 is secured, the entire radio anechoic box 1 is increased in size.

  On the other hand, in the present embodiment, the first inner peripheral surface side wave absorber 5 provided on the inner peripheral surface of the metal casing 2 is configured to absorb electromagnetic waves in the frequency band on the high frequency side. The inner peripheral surface side electromagnetic wave absorber 5 can be separated from the measurement antenna 19 and the like as compared with the inside of the cylindrical member 7. For this reason, it is possible to reduce the coupling between the radio wave absorber 5 and the measurement antenna 19 and the like, to improve the measurement accuracy of the electromagnetic wave, and to reduce the entire radio anechoic box 1. .

  Further, since the radio wave absorbers 3, 5, and 14 are formed in a pyramid shape or a taper shape using a carbon-containing radio wave absorber material, the radio wave absorbers 3, 5, and 14 having a pyramid shape or the like are used on the high frequency side. It can absorb electromagnetic waves.

  On the other hand, since the radio wave absorbers 4, 11, and 15 are formed in a flat plate shape using a ferrite material, electromagnetic waves on the low frequency side can be absorbed using the radio wave absorbers 4, 11, and 15 of the ferrite material. Further, since the second inner peripheral surface side radio wave absorber 11 and the like are formed in a flat plate shape using a ferrite material, the projecting dimension of the radio wave absorber 11 can be reduced, and the inside of the cylindrical member 7 and the like is large. Measurement space can be secured.

  Further, the cylindrical member 7 and the partition member 12 are provided with moving mechanisms 10 and 13 including rails 10A and 13A and wheels 10B and 13B. Therefore, even when the radio wave absorbers 11 and 15 made of ferrite material are heavy, the cylindrical member 7 and the partition member 12 provided with the radio wave absorbers 11 and 15 can be easily moved in the axial direction. For this reason, switching work between the radio wave absorbers 3, 5, 14 and the radio wave absorbers 4, 11, 15 can be performed easily and smoothly, and workability can be improved.

  In the above-described embodiment, the radio wave absorbers 3, 5, and 14 are formed in a pyramid shape or a taper shape, but may be formed in a flat plate shape (sheet shape), for example, as in the related art. In this case, electromagnetic waves in the lower frequency band are absorbed by the radio wave absorbers 3, 5, and 14 provided in the metal housing 2 and the like, and high frequency is absorbed by the radio wave absorbers 4, 11 and 15 provided in the cylindrical member 7 and the like. It is good also as a structure which absorbs the electromagnetic waves of the side frequency band.

  Moreover, in the said embodiment, although the to-be-measured object 17 was set as the structure which radiates | emits electromagnetic waves of two frequency bands, 800 MHz band and 1.9 GHz band, other frequency bands (for example, 900 MHz band, 1.5 GHz band, (2.5 GHz band, 5 GHz band, etc.) may be configured to emit electromagnetic waves.

  In the embodiment, the radio wave absorbers 3, 5, 14 and the radio wave absorbers 4, 11, 15 absorb one different frequency band (1.9 GHz band and 800 MHz band). . However, the present invention is not limited to this. For example, the radio wave absorbers 3, 5 and 14 transmit electromagnetic waves in four frequency bands (1.5 GHz band, 1.9 GHz band, 2.5 GHz band and 5 GHz band) on the high frequency side. The electromagnetic wave absorbers 4, 11, 15 may absorb electromagnetic waves in two frequency bands (800 MHz band and 900 MHz band) on the low frequency side while absorbing. Thus, even when the device under test 17 radiates electromagnetic waves in three or more frequency bands, the characteristics of the device under test 17 can be measured using the single anechoic box 1.

  Furthermore, in the said embodiment, although it was set as the structure which uses a mobile telephone as the to-be-measured object 17, it is good also as a structure which uses the other apparatus which radiates | emits electromagnetic waves. In the above-described embodiment, a biconical antenna is used as the measurement antenna 19, but another type of antenna may be used.

It is a perspective view which shows the electromagnetic wave anechoic box by embodiment of this invention. It is sectional drawing which looked at the electromagnetic anechoic box when measuring the frequency band of a high frequency side from the arrow II-II direction in FIG. It is sectional drawing of the same position as FIG. 2 which shows the electromagnetic anechoic box when measuring the frequency band on the low frequency side. It is sectional drawing which looked at the electromagnetic anechoic box from the arrow IV-IV direction in FIG. It is sectional drawing which looked at the electromagnetic anechoic box from the arrow VV direction in FIG. It is a perspective view which expands and shows the circumference | surroundings of the to-be-measured object in FIG. It is sectional drawing which shows the state which pulled up the to-be-measured object fixing jig and antenna attachment jig in FIG. It is sectional drawing which shows the state which moved the 2nd division | segmentation cylinder in FIG. 7 to the front wall surface side. It is sectional drawing which shows the state which moved the partition member in FIG. 8 to the front wall surface side, and pulled down the to-be-measured object fixing jig. It is sectional drawing which shows the state which moved the cylindrical member in FIG. 9 to the axial direction center side of the metal housing | casing. It is sectional drawing which shows the state which pulled up the to-be-measured object fixing jig and antenna mounting jig in FIG. 3, and moved the cylindrical member to the front wall surface side. It is sectional drawing which shows the state which moved the holding cylinder and the cylindrical member in FIG. 11 to the back wall surface side. It is sectional drawing which shows the state which moved the partition member in FIG. 12 to the back wall surface side. It is sectional drawing which shows the state which moved the holding | maintenance cylinder and the 1st division | segmentation cylinder in FIG. 13 to the front wall surface side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radio wave anechoic box 2 Metal housing 3 1st end surface side radio wave absorber 4 2nd end surface side radio wave absorber 5 1st inner peripheral surface side radio wave absorber 6 Holding cylinder 7 Cylindrical member 8,9 Division | segmentation Cylindrical body 11 Second inner peripheral surface side radio wave absorber 12 Screen member 14 First screen side radio wave absorber 15 Second screen side radio wave absorber 16 DUT to be measured 17 DUT 18 DUT 18 Antenna mounting jig 19 Antenna for measurement

Claims (5)

A metal housing formed in a cylindrical shape with both axial ends closed;
A first end-surface-side wave absorber that is provided on one end surface in the axial direction of the metal casing and absorbs electromagnetic waves in a first frequency band;
A second end face-side radio wave absorber that is provided on the other end face in the axial direction of the metal casing and absorbs electromagnetic waves in a second frequency band;
A first inner peripheral surface side wave absorber that is provided on the inner peripheral surface of the metal casing and absorbs electromagnetic waves in a first frequency band;
A tubular member located inside the metal housing and provided so as to be movable in the axial direction;
A second inner peripheral surface side wave absorber that is provided on the inner peripheral surface of the cylindrical member and absorbs electromagnetic waves in the second frequency band;
A partition in the form of a flat plate located between the first and second end face side wave absorbers inside the metal casing and provided to be movable in the axial direction through the cylindrical member;
A first partition-side radio wave absorber that is provided on a surface of the partition member facing the first end-surface-side radio wave absorber and absorbs electromagnetic waves in a first frequency band;
A radio wave anechoic box formed of a second partition side radio wave absorber that is provided on a surface of the screen member facing the second end face side radio wave absorber and absorbs electromagnetic waves in a second frequency band. The metal casing is provided with an object fixing jig for supporting an object to be measured and an antenna mounting jig for supporting an antenna for measurement,
When measuring the characteristics of the first frequency band, the cylindrical member is disposed on the axial end portion side of the metal casing, the partition member is disposed on the other end face side in the axial direction of the metal casing, And the measurement object fixing jig and the antenna mounting jig are arranged between the first end face side wave absorber and the first partition side wave absorber at a position avoiding the cylindrical member,
When measuring the characteristics of the second frequency band, the cylindrical member is disposed on the axially central side of the metal housing, the partition member is disposed on one side end surface side of the metallic housing, and 2. The measurement object fixing jig and the antenna mounting jig are arranged between a second end face side wave absorber and a second partition side wave absorber at a position sandwiching the cylindrical member. 1. An anechoic box according to 1. The cylindrical member is constituted by a plurality of divided cylindrical bodies that can be divided at an intermediate position in the axial direction,
When measuring the characteristics of the first frequency band, the plurality of divided cylinders are arranged in a state of being separated from each other at both axial ends of the metal casing, and measure the characteristics of the second frequency band. 3. The radio anechoic box according to claim 2, wherein the radio anechoic box is configured to be disposed in a state of being abutted with each other on an axially central side of the metal casing. The first end surface side radio wave absorber, the first inner peripheral surface side radio wave absorber and the first partition side radio wave absorber are configured to absorb electromagnetic waves in the first frequency band on the high frequency side,
The second end surface side radio wave absorber, the second inner peripheral surface side radio wave absorber, and the second partition side radio wave absorber are in a second frequency band on a low frequency side lower than the first frequency band. The radio wave anechoic box according to claim 1, 2 or 3, wherein the radio wave anechoic box is configured to absorb electromagnetic waves. The first end surface side radio wave absorber, the first inner peripheral surface side radio wave absorber and the first partition side radio wave absorber are formed into a pyramid shape or a taper shape using a radio wave absorbing material containing carbon,
5. The radio wave according to claim 4, wherein the second end surface side radio wave absorber, the second inner peripheral surface side radio wave absorber, and the second partition side radio wave absorber are formed in a flat plate shape using a ferrite material. Anechoic box.

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